Going too low for a low bar squat, relaxing stuff to get there, most noticeably your low back/pelvic position. Part of the problem is that you're not actually tight before initiating the lift (looking down does not mean you can't maintain upper back tightness). Big breath + chest up/out before initiating the lift, hold your breath, and maintain your tightness all the way down. Were I training you, I'd whack you in the lower back and remind you to stay tight there at the bottom of the lift.

Also breath through your belly.
Take a big breath, push it down in your belly and flex your abs.
Now you should have a rock hard core.
Move down just below parallel and push up breathing out through pressed lips.
If you fart or shit your pants during your max, your doing it right ;)

Depth at the expense of a tight lumbar position is not fine. The thing is, very few people can go that low in a low bar squat without surrendering their low back position, and as evidenced by the video, the OP is not an exception to this, as his lower back is clearly flexing towards the bottom.

Looking down is fine. The only reason some people frown on it is that, uncoached, a lot of people who look down will also start with a weak upper back position. Hence my advice to get your chest up/out at the top of the movement, take a big breath and hold it to cement that position, and THEN initiate the squat.